Sample preparation and collection tasks are performed in a wide variety of research and testing procedures. As one examples, sampling tasks are performed in conjunction with research relating to pharmaceutical aerosol and powder drug delivery. A popular instrument utilized in this area by those skilled in the art in performing analytical assays is the particle sizing impactor. One specific type of impactor is the multi-stage cascade impactor. The cascade impactor relies on inertial impaction for characterizing aerodynamic particle size distribution of Metered Dose Inhaler (MDI) and Metered Dose Powdered Inhaler (MDPI) products. Such an instrument is useful in that all aerosols can be classified by extensive experimental proofs and empirical verification. Once certain properties of the examined aerosol are known, the cascade impactor can enable comprehensive aerosol definition.
Referring to FIG. 1, a cascade impactor generally designated I typically is constructed of eight to ten classification stages ST that enable, for example, classification of aerosols ranging from 10 to 0.4 :m at 28.3 lpm. In FIG. 1, cascade impactor I includes a stage zero ST0, stages ST1-ST7, a final filter 16, a base element 17, and an inlet cone 18. Each stage ST consists of a jet plate 12 and a stainless steel impaction disc 14 (see FIGS. 10 and 32) or filtration media substrate. Filter 16 collects all particles smaller than 0.4 :m. Pre-separators and other special accessories can be added to allow the cascade impactor to operate at higher flowrates to enable collection of submicron particulate. In FIG. 1, for example, inlet cone 18 is provided for testing of aerosols. A pre-separator 21 (see FIG. 31) would be substituted for inlet cone 18 when dry powders are to be tested. At each stage ST, an aerosol or powder stream passes through the jets of jet plate 12 and around the impaction disc 14. Entrained particles with enough inertia settle upon the impaction surfaces, while smaller particles remain entrained to be deposited upon subsequent stages ST. High jet velocities enable smaller particles to be characterized efficiently. The aerodynamic diameter of the collected aerosol depends upon the jet orifice velocity within each stage ST, the distance between the jets and impaction surface, and the collection characteristics of the preceding jet stage ST.
As is known by those skilled in the art, instruments such as cascade impactor I are employed as part of time-consuming and tedious manual assay procedures. In a typical manual assay, the cascade impaction test includes the following major tasks. Cascade impactor I is assembled and then dosed with the product to be tested. After dosing, cascade impactor I is separated into its individual components. Each stage ST is rinsed with a solvent, and the resulting sample consisting of solvent and particles carried thereby are funneled into a collection container such as a laboratory flask. Additional solvent is then added to dilute the sample to the appropriate volume. The diluted sample is then mixed and assayed by appropriate analytical equipment such as a high-pressure liquid chromatography (HPLC) device.
The desire by those skilled in the art to ameliorate the time and effort required to perform such testing led to the development of the present invention.